Electrophotographic devices are conventionally used widely in which an electrostatic latent image drawn on a photoreceptor by a laser or the like is visualized by a toner or the like and is then transferred to the surface of paper or the like to put into print. In recent years, this toner particle is micronized to improve printing accuracy, and liquid developers (hereinafter also referred to as “liquid toner”) have come to be used which are obtained by dispersing toner particles micronized to, for example, about 1 μm in a liquid called a carrier constituted of such as liquid paraffin, silicon oil, mineral oil or vegetable oil. Consequently, liquid developing electrophotographic devices (see, Patent References 1 and 2 described below) using such a liquid toner have come to be used.
In this liquid developing electrophotographic device, various rollers such as a developing roller, transfer roller, squeeze roller and abrasive roller are used. These various rollers are usually formed by providing an elastic material layer using an elastic material such as a rubber or a resin having a low hardness around the outer periphery of a shaft such as a core bar.
However, such a roller is used in a circumstance where it is in direct contact with the carrier mentioned above and is exposed to vaporized carrier in this liquid developing electrophotographic device.
Therefore, there is such a problem that, for example, the rubber or resin used for forming the elastic material layer of the roller is, for example, swollen in the carrier, causing a variation in the volume of the elastic material layer.
When the elastic material layer of this liquid developing electrophotographic device roller is varied in volume, the contact pressure, nip width and the like between these rollers are varied, resulting in low printing accuracy.
For this reason, for the liquid developing electrophotographic device, a roller having suppressed in volumetric variation caused by a carrier is required. However, the conventional liquid developing electrophotographic device roller is only insufficiently suppressed in volumetric variation caused by a carrier and does not reach the level at which the aforesaid requirements are satisfied.
Specifically, the conventional liquid developing electrophotographic device is insufficiently suppressed in a deterioration of printing accuracy accompanied with a variation in the volume of the liquid developing electrophotographic device roller.
Patent Reference 1: Japanese Unexamined Patent Publication No. 2003-057913
Patent Reference 2: Japanese Unexamined Patent Publication No. 2005-070181